The present invention relates to an air conditioning apparatus for a vehicle and, more particularly, to a system for controlling the amount of outside air introduced into a ductwork of the apparatus in a cooling mode of operation.
An air conditioning apparatus for a vehicle generally includes a blower to force air selected by an outside/recirculated air selector door into a ductwork. Air forced through the duct is cooled or heated and suitably proportioned by an air mix door which is swingable in the duct to control the air flow path. The proportioned air mixture is blown out of the duct into a cabin of the vehicle.
A prior art air conditioning apparatus of the type described above is operated in a cooler mode by first turning on a compressor operation switch to cool air in the duct which consists of recirculated air only. It is only after the temperature inside the vehicle cabin is lowered approximately to a preset level that outside air whose proportion is limited is introduced into the duct to be mixed with the recirculated air. This sudden supply of outside air, which will be hot, after the drop of the cabin temperature gives occupants of the vehicle unpleasant sensations. As is often the case with cars, the temperature in the vehicle cabin rises beyond the outside temperature level when the vehicle is left a long period of time under intense sunlight as in summer time. When the compressor is activated despite such a high temperature inside the vehicle cabin, it must work against an excessive load in an initial stage of the cooling operation and this will shorten its service life. Additionally, the apparatus needs a substantial period of time to cool off the air inside the cabin after being turned on. It will be apparent that the uneasy feelings caused by the aforesaid sudden supply of outside air in a cooling mode are more pronounced.